1. Field of the Invention
The present invention relates to a process of controlling a direct-drive robot.
2. Statement of the Related Art
Recently, various kinds of robots have been used in automated factories, and in particular, direct-drive robots have been developed in order to satisfy the demands of high speed and high accuracy.
Referring to FIG. 5 which shows a block diagram of a control system used with respect to a conventional robot as one example, a position command section 1 delivers a command value to a subtractor 3 which then subtracts a value delivered from an up-down counter 2, from the command value. The result of the subtraction is delivered to a DA converter 5 which converts the same into an analog value that is then amplified by an amplifier 6. The amplified value is then applied to a speed instructing type motor drive 7 for controlling a motor 8 which therefore runs at a speed proportional to the output of the amplifier 6.
However, with the use of the above-mentioned conventional arrangement for controlling a direct-drive robot arm, it has been necessary to increase the a gain of the amplifier in order to enhance the servo rigidity thereof if the arm is in a stop condition in which the positional deviation is small, resulting in generation of a slight vibration. Also, upon deceleration or acceleration which causes the positional deviation to be large due to follow-up deviation, the gain has been decreased so as to avoid overflow of the DA converter, resulting in lowering the positional accuracy.